In automatic concrete block-making machines, the blocks are molded on the upper surfaces of flat, steel pallets supplied from a pallet magazine to the molding section of the machine. After molding, the pallets, with newly formed blocks on them, are moved out of the machine to a point where the blocks are cured. After curing, the blocks are removed from the pallets which then are returned to the pallet magazines for reuse in the cycle of operation of the machine.
After blocks have been formed on a pallet, there is a build-up of aggregate concrete flash which sticks to the pallets; and if the pallets are continuously reused without removing this flash, a substantial build-up of encrusted material develops. This build-up material results in misshapen blocks and further can interfere with the most efficient operation of the concrete block-making machine. Therefore, the flash must be removed. Often, this is done by periodically running all of the pallets through a separate pallet-cleaning machine. This results in lost down time and expense while the pallets are being cleaned. In addition to the down time, there also is a substantial expense incurred in the provision of such separate cleaning machines. Generally, they require additional motors; cams, or hydraulic controls; belts or chain drives; and necessarily must be of relatively heavy construction because of the nature of the operation being effected by them. Consequently, such machines are not readily portable and are relatively expensive.
A typical stand-alone machine for cleaning pallets is shown in the Patent to Frese, U.S. Pat. No. 2,799,879. This machine requires a separate motor and reciprocating pallet transport mechanism to move the pallets beneath a spring-loaded scraper blade which is urged downwardly onto the pallet surface by a number of stiff compression springs. Because of the substantial downward force exerted on the pallet, the mechanism for moving the pallet beneath the scraper blades necessarily is a heavy duty mechanism. The pallets are fed one at a time into the device, and the scraper blade is raised momentarily as each new pallet is moved into position beneath the blade. After the pallet is in position, the blade is lowered onto the palet surface which then is moved beneath the blade for cleaning. The machine of Frese is expensive, and it is not intended as a continuous cleaning machine used in conjunction with the pallet-feed mechanism of an automatic concrete block-making machine. Consequently, pallets which are becomeing increasingly encrusted with aggregate are allowed to accumulate until the periodic cleaning of such pallets is effected from time to time in a machine such as shown in the Frese Patent.
In an attempt to clean pallets each time they are fed from a pallet magazine to the molding section of a concrete block-molding machine, a variety of pallet-cleaning devices have been developed in the past. One such device is disclosed in Patent No. 3,217,348. This device is a transverse reciprocating scraper blade driven by a separate motor which moves the blade back and forth across the pallet as the pallet moves in its path from the pallet magazine to the molding portion of the machine. The motor which drives the scraper blade is synchronized in its operation to start and stop in conjunction with the machine operation, and the mechanism includes additional cam and roller assemblies for raising and lowering the pallet cleaner frame as pallets are moved beneath and through the pallet cleaner portion of the machine. A large number of additional moving parts are required in this relatively cumbersome device, thereby, subjecting it to the potential of substantial maintenance expense and down time.
An attempt at a static "plow-shaped" pallet scraper is disclosed in U.S. Pat. No. 2,752,621. This pallet scraper mounts two pallet-scraping blades at an angle 90 degrees to one another with the point pivotally mounted adjacent the pallet magazine from which the pallets are fed as they pass through the machine. Long, rigid blades are employed, and the device has a frame which is spring biased downwardly to apply pressure to the surface of pallets moving beneath it. If a pallet passing through the device is warped, incomplete cleaning occurs, and the heavy downward force applied to the pallet also places a substantial strain on the conveyor mechanism for moving the pallet through the device.
Another pallet-cleaning device employed in the past is shown in U.S. Pat. No. 2,637,057, which requires a special driving mechanism and operates to reciprocate a pallet-scraper blade transversely back and forth across the pallet as it travels through the machine. In this respect, this machine is similar in its operation to the machine shown in U.S. Pat. No. 3,217,348. Rotating the scraper blades is shown in U.S. Pat. No. 1,045,677, and chipping and vibrating pallet-cleaning devices are shown in U.S. Pat. Nos. 2,724,137 and 3,110,050. All of these patents require additional moving, mechanical parts in order to accomplish the cleaning operation.
None of the above patents have a provision for protecting the blades of the pallet-cleaning devices in the event the mechanism for moving the pallet should reverse from its normal direction. Such reversal, however, occurs frequently in the operation of concrete block-making machines and causes chipping or breaking off of the scraper blades, for example, when it occurs in a machine such as the one shown in U.S. Pat. No. 3,217,348.
It is desirable to provide a pallet cleaning or scraping device which is relatively inexpensive, which works continuously in conjunction with the operation of a concrete block-making machine, which applies minimum forces in the direction of travel of pallets through the machine to thereby reduce the strain on the pallet moving mechanism, and which is not subject to damage in the event of an intentional or accidental reversal of direction of travel of pallets through the pallet cleaning device.